The present invention relates to photosensitive compositions and, in particular, to such compositions suitable for the production of printing plates. Specifically, the invention relates to such compositions comprising diazonium salt polycondensation products and a polymeric binder.
German Offenlegungsschrift No. 2,024,244 (corresponding to U.S. Pat. No. 3,867,147) discloses photosensitive recording materials comprising cocondensation products of condensible diazonium salts and other non-photosensitive condensible compounds, optionally combined with polymeric binders, which are used for producing printing plates. These photosensitive materials are distinguished by their high photosensitivity and good print runs. The print run obtained is particularly large if water-insoluble binders, for example, polyvinyl formal, are used, but such layers can only be properly processed by means of developers containing a considerable amount of volatile organic solvents.
German Offenlegungsschrift No. 3,130,987 describes similar compositions which comprise styrene-maleic anhydride copolymers as the binders and which can be developed with purely aqueous alkaline solutions. These binders usually have acid numbers well over 100. The printing plates obtained using these compositions, however, yield print runs which are inferior to those of printing plates containing binders which are insoluble in aqueous alkaline solutions.
German Offenlegungsschrift No. 3,036,077 discloses corresponding compositions which contain binders comprising polymers with alkenylsulfonylurethane side groups. These compositions can also be developed by means of purely aqueous solutions. However, when the compositions are processed to form lithographic printing plates, they yield light cured coatings, in which ink receptivity is insufficient.
From U.S. Pat. No. 2,861,058, photosensitive polymers are known, having cinnamate and dicarboxylic acid monoester side groups. These polymers contain a relatively high amount of acid groups, corresponding to acid numbers from at least 100 to about 300, in order to render the coatings soluble in aqueous alkaline solutions.
In German Offenlegungsschrift No. 2,751,060, photosensitive compositions are described which comprise a photosensitive resin and a cellulose ether dicarboxylic acid halfester. These compositions are used in the production of photoresist coatings and have the advantage of a good etch resistance. Due to the strongly hydrophilic nature of the cellulose which serves as the parent substance, the oleophilic character of these polymers is, in most cases, inadequate for use in the printing image areas of printing plates. Moreover, since the cellulose molecule has a given molecular size and structure, it is difficult to vary its properties to a sufficient extent by substitution.